The invention relates to a method and an apparatus for determining the position and the orientation of an eye.
Such methods and apparatuses are used in particular during refractive eye surgery, wherein the total refractive power of the eye can be altered and conventional optical corrections such as spectacles or contact lenses can ideally be obviated thereafter. Particularly during laser ablation for changing the corneal curvature, wherein generally an ablation laser beam is guided over the curved surface of the cornea, during the treatment it is necessary to know the exact position of the eye and also the orientation of the eye—that is to say the orientation of the eye with respect to three angles in space. The position of the eyeball in a Cartesian coordinate system with the coordinates X, Y and Z and also the orientation of the eyeball in relation to three spatial angles Rollx, Rolly and Rollz are defined as follows in accordance with FIG. 2:
The Cartesian coordinates X, Y and Z are chosen such that the Z-axis substantially coincides with a laser processing axis A3 and is oriented in the viewing direction. The X-axis is oriented such that the X-axis coincides with the horizontal when a person is standing upright. Correspondingly, the Y-axis is arranged vertically. The spatial or rotation angles of the eyeball are defined in a manner corresponding to the Cartesian coordinates as roll angles Rollx, Rolly and Rollz. The angle Rollz is also called cyclotorsion.
One option for capturing the position and orientation of the eye consists in recording a camera image of the surface of the eye. The evaluation of the camera image has to take account of all possible movements of the eye during such an operation.